Nano engineered eggshell flexible biopolymer blend and methods of making biopolymer blend film and using such bioplastic blends for improved biodegradeable applications

ABSTRACT

A biopolymer blend is provided that comprises a combination of three components: poly (butylene adipate-co-terephthalate) (PBAT); agriculture sourced polylactic acid (PLA); and engineered proteinaceous eggshell nanoparticles. The two polymer components can be present in any ratio but an approximate 70:30 ratio is preferred. The engineered proteinaceous eggshell nanoparticles are preferably about 10-25 nanometers. Also provided are methods of preparing biopolymer film and packaging components. Pelleted poly (butylene adipate-co-terephthalate) and agriculture sourced polylactic acid (PLA) are dissolved in chloroform and mixed together to form a polymer blend, and engineered proteinaceous eggshell nanoparticles are incorporated into the polymer blend, which is then extruded to create a biopolymer film or component.

This application claims priority to U.S. provisional application62/535,014, filed on Jul. 20, 2017 and is herein incorporated byreference in its entirety.

This invention was made with government support under contract no.NSF-RISE 1459007 awarded by National Science Foundation. The governmenthas certain rights in the invention.

FIELD OF THE INVENTION

The present invention relates to flexible biopolymer blends, andspecifically to a nano engineered eggshell flexible biopolymer blend,and more specifically to engineered proteinaceous eggshell nanoparticlesblended with poly(butylene adipate-co-terephthalate)/polylactic acid tocreate flexible films and packaging components.

BACKGROUND

Biodegradable poly (lactic acid) (PLA) sourced from renewable resourceshas received attention in polymeric material design industry because offavorable characteristics, including a good degree of biodegradability,biocompatibility, high mechanical strength and excellent processability.Potential sources of PLA include a wide range of agriculture basedrenewable sources, such as corn starch, tapioca roots, chips or starch,or sugarcane. Due to its reasonable performance and availability in themarket at a reasonable price, PLA has been considered a promisingsubstitute to petroleum-based recalcitrant plastics in commercialapplications, such as packaging and fiber materials. Deficiency in theductility of PLA, however, significantly limits its use in applicationssuch as in packaging and automotive industries. It is well-known in thematerial science and packaging industry that inferior durability and lowthermal resistance are characteristics that hinder the broader use ofPLA in these industries. Additionally, PLA exhibits extreme brittleness,with only a 5% fracture strain in tensile testing, which results in poorimpact and tear resistance. A problem exists then from a structuraldesign prospective, preventing the use of PLA as a promising substitutefor petroleum source thin films and packaging components.

Attempts have been made to offset inferior PLA film properties,including the creation of PLA blends, such as Poly (lactic acid)/Poly(ether-b-amide) PLA/PEBA blends, PLA/PBAT blends, Poly (1-lactide)(PLLA) and poly (ϵ-caprolactone) (PCL) PLLA/PCL blends, PLA/castor oil,PLA/PCL and Poly(lactic acid)-Poly(hydroxybutyrate) PLA/PHB. Desirablemechanical properties, however, were not achieved by any of these blendsdue to the immiscibility of the two chemically diverse polymers, thusthwarting efforts to blend these components. Further efforts were madeto attain desirable properties or improved PLA film properties,including the compatibilization, or modification of the microstructurethrough the introduction of a third component, which is a commonpractice in polymer blending to increase stability of an immiscibleblend of polymers. Although the use of nanomaterials has shown somepromise in this regard, biopolymer blends using an economical andbiocompatible naonmaterial has not been identified.

For example, polylactide/poly [(butylene succinate)-co-adipate](PLA/PBSA)-organoclay composites were prepared via melt compounding in abatch mixer to determine the effect of clay on the properties of theblend. PLA/PBSA 70:30 blends with varied weight fractions of theorganoclay (0 to 9%) were prepared and analyzed. Thermal analysisrevealed that crystallinity was dependent on the clay content localizedwithin the matrix of the composite. On the other hand, thermal stabilityslightly improved for composites with less than 2 wt. % clay content asagainst the deterioration observed in composites with clay contentgreater than 2 wt. %. Tensile analysis also revealed that a compositewith 2 wt. % clay content possesses a slight improvement in elongationat break by 29% due to the alteration of the interfacial properties bythe clay to favor ductility in the PLA/PBSA blends. Additional studiesreported the effect of blending PLA/PCL with TiO2 nanofiller, includingthe effects on the thermal stability and degradation behaviors of thepristine and blended polymers. It was observed that nano-TiO2preferentially aligned onto the PLA phase in the immiscible blend, dueto large differences in the relative polarities between PLA and the TiO2which led to low surface tension (2.0 mNm⁻¹) and high force ofattraction between them. Also, improvement in thermal stability of theblend was observed, due to the action of nano-TiO2 as a fire retardantto impede combustion. The dynamic mechanical properties of PLA/PHBV,PLA/PCL and PHBV/PCL blends in the absence and presence of nano-TiO2have also been evaluated. The storage modulus in the glassy region ofthe PHBV/PLA blend showed improvement over those of the pristinepolymers with very minimal effects attributable to the nano-TiO2. Thissuggested partial interfacial miscibility between the two polymers.However, the dynamic mechanical analysis (DMA) for PLA/PCL and PHBV/PCLpolymer blends show insignificant influence due to blending andnano-TiO2 inclusion. The reinforcing effects of eggshell particles havebeen investigated in some polymers and polylactic acid blends, however,blends with engineered proteinaceous eggshell nanoparticles (PENP) andthe improved properties thereof have not been investigated.

Therefore, there still remains a need for a PLA-based biopolymer blendalternative to the PLA films that will result in an agriculture sourcedPLA blend with improved properties such as greater heat resistance,durability, permeability. It would also be desirable to provide abiopolymer blend with improved compostability and biodegradability. Theinvention meets these needs.

SUMMARY OF THE INVENTION

A biopolymer blend is provided comprising a combination of threecomponents: poly (butylene adipate-co-terephthalate)(PBAT); polylacticacid (PLA); and engineered proteinaceous eggshell nanoparticles (PENP).

Preferably, the amount of PENP is used between 0.5 to 2.0% wt of thebiopolymer blend.

The two polymer components a) and b) can be in any ratio blend but anapproximate 70:30 ratio is preferred.

The polylactic acid is preferably derived from a renewable agriculturebased source.

The engineered proteinaceous eggshell nanoparticles are preferable about10-25 nm.

Also provided is a method of preparing biopolymer blend film. Poly(butylene adipate-co-terephthalate)(PBAT) and agriculture basedpolylactic acid (PLA) are mixed in chloroform to form a polymer blendand engineered proteinaceous eggshell nanoparticles are incorporatedinto the polymer blend to form a polymer nanoparticle blend. The polymernanoparticle blend is extruded to form a biopolymer film.

Preferably the amount of polymer blend is a PBAT to PLA ratio of 70:30.Further, the amount of proteinaceous eggshell nanoparticles used in thepolymer nanoparticle blend to form the biopolymer film is between 0.5 to2% by weight of the polymer nanoparticle blend. The PBAT/agriculturesourced PLA blend that incorporates between 0.5 to 2.0% wt. ofengineered proteinaceous eggshell nanoparticles (PENP) creates amiscible blend with improved thermal stability, flexibility, anddurability.

A method of preparing a biopolymer blend packaging component is alsoprovided. Poly (butylene adipate-co-terephthalate)(PBAT) and agriculturebased polylactic acid (PLA) are mixed in chloroform to form a polymerblend and engineered proteinaceous eggshell nanoparticles areincorporated into the polymer blend to form a polymer nanoparticleblend. The polymer nanoparticle blend may be extruded to form apackaging component.

Preferably the amount of polymer blend in the method of preparing apackaging component is a PBAT to PLA ratio of 70:30. Further, the amountof proteinaceous eggshell nanoparticles used in the polymer nanoparticleblend to form the packaging component is between 0.5 to 2% by weight ofthe polymer nanoparticle blend that is useful to create flexible filmsand composites.

The invention also provides an agricultural sourced PLA-based blend thatincorporates engineered proteinaceous eggshell nanoparticles (PENP) tocreate flexible films and packaging components and products. Anadditional benefit of using an engineered proteinaceous eggshellnanoparticle is to utilize eggshells as an economic source ofnanoparticles that also reduces bio-waste. The inherent carboxylicgroups from organic templates on which the eggshell crystals aredeposited are well exposed to interact with materials with likefunctionalization, due to high surface areas. Poly (butyleneadipate-co-terephthalate) (PBAT) and PLA are both polyesters, sincethese groups are compatible with the carboxylic groups in the eggshellparticles, they can likely enhance the interfacial barrier between PBATand PLA to improve structural integrity.

The invention also provides a PBAT/agriculture sourced PLA blend thatincorporates engineered proteinaceous eggshell nanoparticles (PENP) witha nanoparticle size that is between 10-25 nanometers. Also provided is amethod of making biopolymer films and packaging components derived froma PBAT/agriculture sourced PLA blend that incorporates engineeredproteinaceous eggshell nanoparticles (PENP) with a nanoparticle sizethat is between 10-25 nanometers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of X-ray diffraction (XRD) patternstructural analysis of eggshell nanoparticles.

FIGS. 2A-2C illustrate transmission electron micrographs of thesynthesized PENP: FIG. 2A High magnification; FIG. 2B plate-likestructure; and FIG. 2C low magnification analysis.

FIGS. 3A-F provide X-ray diffraction patterns of the following PLAblends: FIG. 3A PBAT/PLA 70/30; FIG. 3B PBAT/PLA/PENP 70/30/0.5; FIG. 3CPBAT/PLA/PENP 70/30/1; FIG. 3D PBAT/PLA/PENP 70/30/1.5; FIG. 3EPBAT/PLA/PENP 70/30/2; and FIG. 3F PENP.

FIG. 4 provides Raman spectra analysis of the following: line (a) showsthe results for PENP; line (b) shows the results for PBAT/PLA 70/30 andline (c) shows the results for PBAT/PLA/PENP 70/30/1.

FIG. 5 provides differential scanning calorimeter (DSC) curves for PENPand PBAT/PLA/PENP blend composites.

FIG. 6 illustrates thermal degradation analysis of PENP andPBAT/PLA/PENP blend composites.

FIGS. 7A-D provide tensile analysis of PBAT/PLA/PENP blend composites,including: FIG. 7A stress versus strain curves; FIG. 7B tensilestrength; FIG. 7C elastic modulus; and FIG. 7D strain at maximum load.

FIGS. 8A-D include scanning electron microscopy (SEM) micrographs offractured surfaces after tensile analysis of PBAT/PLA 70/30 at FIG. 8Alow and FIG. 8B high magnification and PBAT/PLA/PENP 70/30/1 at FIG. 8Clow and FIG. 8D high magnification.

FIG. 9 provides a PBAT structure.

FIG. 10 illustrates the process of making a PLA structure.

FIG. 11 includes examples of extruded polymer blend films.

FIG. 12 provides an example of a 3D printed polymer blend film.

DETAILED DESCRIPTION OF THE INVENTION

The invention described herein relates to a biopolymer blend comprisinga combination of three components: poly (butyleneadipate-co-terephthalate) (PBAT); polylactic acid (PLA); and engineeredproteinaceous eggshell nanoparticles (PENP). This biopolymer blend hasdesirable characteristics, including increased thermal stability,increased tensile strength, and improved durability. If using a PBAT orPLA alone, the biopolymer is brittle and lacks desirable mechanicalproperties. Additionally, a PBAT/PLA blend creates an immiscible blendwhich also lacks the mechanical properties needed to create a flexiblebiopolymer blend. Specifically, a PBAT/PLA blend does not have tensilestrength due to poor interaction between the phase separated polymers.Therefore a biopolymer blend that incorporates PENP results in abiopolymer/PENP blended composite with improved characteristicsincluding increased thermal stability, tensile strength and durability.

The PBAT and PLA can be sourced from agricultural sources at low cost.PLA is derived from fermenting various sources of natural sugars fromannually renewable agricultural crops such as corn, sugar beets, andsugarcane. Additionally, the synthesis of engineered proteinaceouseggshell nanoparticles (PENP) provides a use for chicken eggshellbiowaste. Worldwide million tons of chicken eggshells are generated asbiowaste daily. Each eggshell represents approximately 11% of the totalweight of the egg and is comprised of three components: calciumcarbonate (about 94%), organic matter (about 4%) and calcium phosphate(about 1%). In addition to being a plentiful and economic source ofmaterial, PENP made as described herein are relativity inexpensive tomanufacture. Therefore the combination of the inexpensive biopolymerswith the synthesized PENP results in the production of an economicalbiopolymer film or biopolymer composite. Further, the resultingbiopolymer film and biopolymer composite provides a positiveenvironmental impact in that the biopolymer PENP blend is compostableand biodegradable.

The biopolymer blend may have two polymer components, poly (butyleneadipate-co-terephthalate)(PBAT) and polylactic acid (PLA), in a 80:20,70:30 or 50:50 ratio, preferably in a 70:30 ratio. The ratio may rangefrom 90:10 to 50:50.

The amount of PENP incorporated into the biopolymer blend is between 0.5to 2.0% wt of the biopolymer blend. The preferred amount PENP in thebiopolymer may range from between 0.5 to 1.0%. The optimized amount ofPENP incorporated into the blend is 2.0% of weight for significantcrystal nucleation.

The biopolymer blend, including any of the preferred blends, may includecolorants. Colorants used in the biopolymer blends may be used to addcolor to the films, to print bar coding or any other means ofidentification.

The biopolymer blends may also be formed as printed film or packagingcomponents using 3D printing capabilities.

Engineering Proteinaceous Egg Shell Nanopowder (PENP)

Chicken eggshells with the inner protein layer (organic matter) weredried at room temperature for 48 hours and crushed using a mortar andpestle. Proteinaceous egg shell nanopowder (PENP) was prepared by a ballmilling technique and followed by ultrasonic irradiation as describedherein. The resulting engineered eggshell particles are in micron sizeand provide high surface areas. Preferably the proteinaceous egg shellnanopowder is comprised of particles are less than 100 nm in size,highly crystalline, irregular and porous. More preferably, the particlesare between 10-25 nm in size. Further, the atomic arrangement of thePENP crystals is also a highly aligned pattern arrange single layers ofplate-like structure(s). This arrangement allows the PENP to alignbetween the biopolymer blend molecules, leading to enhancement of thecomposite mechanical properties.

In addition, the eggshell particles include carboxylic groups that arecompatible with the biopolymers PB HAT and PLA, which are bothpolyesters. The PENP enhance the interfacial barrier between PBAT andPLA to improve structural integrity of the composite.

Biopolymer Blending

In order to enhance the bioflexibility and strength of PLA, blending canbe carried out with poly(butylene adipate-co-terephthalate) (PBAT) togenerate PBAT/PLA blend using conventionally accepted melt blendingprocesses and solution blending, preferably melt blending is utilized.The PENP was mixed with the biopolymer blends to ensure homogenousdistribution of the PENP throughout the biopolymer components usingstandard mixing methods as described herein and precipitated and vacuumfiltered.

Extrusion of the Biopolymer Composite to Form Biopolymer Film

The precipitated biopolymer blends containing the dispersed PENP areformed into biopolymer films or components using standard extruderequipment. This extruder equipment contains thermostat control fiveheating zones and screw rotational speed to facilitate melting, mixingand the formation of continuous viscous melt for the extruded film.Optimum working temperatures were maintained at 320, 320, 320, 315 and312° F., for the barrel and die zones. High barrel temperature arefavorable to allow the polymer to melt and randomly orient theparticulates within the flowing matrix whiles the screw rotation induceshigh velocity in the matrix, causing immense shear force whichcontributes to the random distribution of the particles. The biopolymerfilms are between 0.1-0.3 mm thick blend composite specimens.

The precipitated biopolymer blends containing the dispersed PENP arealso formed into biopolymer films using 3D printer applications tocreate biopolymer films instead of traditional extruding methods.

The resulting biopolymer films or components have improved thermalstability or resistance to temperature induced degradation in thematerial, making these biopolymer films ideal with use in a wide rangeof industrial applications, including, but not limited, to foodpackaging, including vegetable packaging, food catering products,organic waste or trash bags, biodegradable diapers, and biomedicalpackaging.

Experiments

The various experiments described herein illustrate the compositions andproduction of compostable poly (butylene adipate-co-terephthalate)(PBAT)/agriculture sourced polylactic acid (PLA) blend compositions,films and composites with 0.5-2.0% proteinaceous eggshell nanoparticles(PENP) for the production of enhanced biopolymer blended films andpackaging components. These experiments also provide support for theeffectiveness of PENP on the microstructure, thermal and tensileproperties of biopolymer or bioplastic blends and components. Further,these experiments demonstrate an improved composition with improvedcharacteristics that also has a positive environmental impact byutilizing eggshells, which are normally considered bio-waste.

Polymer Blend Materials and Method of Making Polymer Blends

Poly (butylene-co-adipate terephthalate) (PBAT) (Ecoflex F blend C 1200)and biopolymer GF-106-02 were obtained as a research samples from BASFCorporation, Villa Park, Ill., USA and Biotec GmbH & Co KG, Emerich,Germany respectively. Whiles the polylactic acid (PLA) (Ingeo™biopolymer 3051D) was obtained from NatureWorks LLC, Minnetonka, Minn.,USA. Eggshells were obtained from American dehydration foods Inc.,Atlanta, Ga., and processed to eggshell nanoparticles. Chloroform(CHCl3, ≥99%) used to dissolve the pelleted polymers and was of hplcgrade, methanol (CH3OH, ≥99.9%), used to precipitate the blend/PENPmixture, polypropylene glycol (PPG) used as a liquid medium for the ballmilling of eggshells and denatured reagent grade ethanol (CH3CH2OH) usedfor washing the PPG and for ultra-sonication were all purchased fromSigma Aldrich, St. Louis, Mo.

Processing of Proteinaceous Eggshell Nanoparticles

Eggshells with the inner protein layer were dried as received at roomtemperature for 48 hours and crushed using a mortar and pestle.Proteinaceous egg shell nanopowder (PENP) was prepared by ball milling 5grams of the micro particles in 10 mL of PPG with 8 steel balls (6 mm)using Spex Sample prep 8000D mixer/mill for 10 hours. The product wasthen washed 4 times with absolute CH3CH2OH and centrifuged for 5 min at15000 rpm (Allegra 64R, Beckman Coulter). The resulting product wasagain mixed with 50 mL of CH3CH2OH and magnetically stirred at 1200 rpmfor 30 min, then ultrasound irradiated for 5 h (Sonics vibra cellultrasound, Model WCX 750, Ti-horn 20 kHz, 100 W/cm²) at 50% amplitudeand 25° C. The PENP/CH3CH2OH suspension was then centrifuged at 15000rpm. The supernatant was separated and the PENP vacuum-dried for 12hours.

Incorporation of PENP into Biopolymer Blend Systems

In order to homogeneously mix the PENP with the polymer blend, 150 g ofthe 70/30 PBAT/PLA solution was blended in 500 mL of CHCl3 by magneticstirring for at least 12 hour at 400 rpm on magnetic stirrer/hot plate(CIMAREC, Barnstead International). Specific amounts of the PENP wasadded to make 2, 1.5, 1.0 and 0.5 percent by weight of the blend wasfirst dispersed in 60 mL CHCl3 on a magnetic stirrer (Sigma Aldrich, IKAWORKS, Inc.) at 600 rpm for 30 minutes before it was added to each meltblend and allowed to mix for an additional 4 hours. After this, theblends and the PENP were further homogenized by mechanical stirring for5 minutes, before excess (800 mL) CH3OH was added in steps of 100 mLwhiles mechanical stirring to precipitate the mixture into solid powderthrough a methanolysis process (breakdown of chloroform to release thepolymer using methanol). After the precipitation, the mixture was allowfor additional 2 hours to ensure complete methanolysis of chloroformbefore the powder was vacuum filtered (100 mm Whatman™) for 20 minutesand dried at 40° C. for 12 hours in an oven (Isotem 200 Series).

Extrusion of the Polymer Blend Composites

About 150 g of each of the precipitated blends containing the dispersedPENP was dried for 12 h at 140° F. in a hopper (DRI-AIR Industries Inc.,model RH5). This was then fed into a19 mm (diameter) table top singlescrew extruder (Wayne SN: 8001) which is driven by 2 hp motor.Thermostat control five heating zones and screw rotational speedfacilitated the melting, mixing and the formation of continuous viscousmelt for the extrudate. Three heating zone are located in the barrelwhiles two are in the die zone. The optimum working temperatures weremaintained at 320, 320, 320, 315 and 312° F., for the barrel and diezones respectively. High barrel temperature causes the polymer to meltand randomly orient the particulates within the flowing matrix whilesthe screw rotation induces high velocity in the matrix, causing immenseshear force which contributes to the random distribution of theparticles. About 40 mm wide and 0.1-0.3 mm thick blend compositespecimens were obtained at a screw speed of 20 rpm and a feed rate of4.4 g/minutes and collect at the die orifice. The continuous hot moltenfilms were passed through water stationed at the orifice of the die forquenching. These blends were stored in a high vacuum desiccator (JOEL,EMDSC-U10A) and only removed during characterization as needed.

Characterization of the Polymer Blend Composites

Raman Analysis

Molecular vibrational spectroscopic analysis of the pristine and blendedpolymer systems were achieved through the use of DXR Raman microscopy(Thermo Scientific). This test was done using 532 nm laser (5.0 mWpower), filter and grating. OMNIC Software was used for data acquisitionand analysis. The essence in the vibrational analysis is to assist inthe identification of functional groups identical to each pure polymerin the blend, any form of phase change and type of interactionsoccurring between the blend systems.

X-Ray Diffraction (XRD)

X-ray diffraction analysis was performed on all specimens, using aRigaku diffractometer (DMAX 2100) equipped with Cu Kα radiation,operated at a step size of 0.02°, scan rate of 10°/minutes, 3° to 80°Braggs angle of diffraction and 40 kV to 30 mA.

Transmission Electron Microscopy (TEM)

Transmission electron microscope (TEM- Joel 2010) was used to determinethe particle sizes and morphologies of the prepared PENP. One (1) mg ofthe ENP specimen was disperse Joel 2010 microscope d in 5 mL CH3CH2OHfor 10 minutes in an ultrasonic bath and a drop of the colloidalsolution was deposited on a copper grid for analysis.

Differential Scanning Calorimetry (DSC)

A TA Q 2000 differential scanning calorimeter (DSC) was used to studythermal profiles of the specimens. Samples of 10.0±0.1 mg were used inthe test. Each sample was sealed in aluminum pan and the test runagainst an empty reference pan. Each specimen was cooled at 20.0°C./minutes from room temperature to −40° C. and subsequently heated from−40° C. to 200° C. at 5° C./minutes and held at constant temperature for2.0 minutes to erase previous thermal history. It was again cooled from200° C. to −40° C. at 20.0° C./minutes before finally scanning at 5.0°C./minutes from −40° C. to 200° C. to determine the various heattransitions in each specimen.

Thermogravimetric Analysis (TGA)

Thermogravimetric analysis was carried out with TA Q 500 equipment.Samples of 14±0.2 mg were place in platinum pans. An empty platinum panwas used as a reference. Each sample was heated from 30° C. to 600° C.in a 50 mL flow of N2. A heating rate of 5° C./minutes was used and thecontinuous records of sample temperature, mass, first derivative andheat flow were taken.

Tensile Testing

Measurement of tensile mechanical properties was performed using ZwickRoell Z2.0 mechanical testing system in accordance to ASTM D 882 using acrosshead speed of 500 mm/minutes and 2.5 kN load cells and wedge grips.Specimens were cut from the extruded sheets of polymer systems 19 mm×0.3mm×120 mm. The test was conducted at 20 mm gauge length with TestXpertdata acquisition and analysis software. At least 15 specimens weretested and averaged in to the reported mechanical properties.

Scanning Electron Microscopy(SEM)/Energy Dispersive Spectroscopy

Microstructure and blend morphologies were probed using Joel JSM-5800Scanning electron microscopy (SEM). Film samples were cut and placed ona carbon tape on 4-in wide sample holder of the SEM. This was thensputter coated with gold-palladium for 5 minutes in Hummer 6.2sputtering system purged with N2 gas and operated at 20 millitorr, 5volts, and 15 milliamps. Fractured surfaces of the tensile specimenswere examined using Hitachi S-3400N SEM and EDS analyses were done inthe back scattering mode.

Transmission Electron Microscopy (TEM) and X-Ray Diffraction Results

Results of the X-ray Diffraction are shown in FIG. 1. In particular,FIG. 1 is the XRD pattern of the synthesized PENP and the standard file#47-743 of calcite from the Joint Committee for Powdered Diffraction(JCPDS) data base. The nature of the diffraction peaks suggests that theinorganic phase is highly crystalline with crystal sizes in thenanometer range due to the broader nature of the peaks.

FIG. 2 provides the results of the Transmission Electron Microscopyanalysis. In particular, FIG. 2A shows that the particles are less than100 nm (10-25 nm) in sizes, highly crystalline, irregular and porous.The crystallinity of the PENP is clearly provided in the crystal latticeshown in FIG. 2B. In addition, FIG. 2B shows the atomic arrangement ofthe crystals in a highly aligned pattern arrange in layers of plate-likestructure. This is important because the inorganic material can adoptthis type of arrangement to align in between polymer molecules, leadingto enhance in mechanical properties.

FIG. 3 shows the morphology of the blends and the pure systems analyzedby X-ray diffraction. Diffraction patterns of a PBAT/PLA 70/30 blend(FIG. 3A), PBAT/PLA 70/30 blend composites (FIG. 3B-E) and PENP (FIG.3F) are provided. A semi crystalline diffraction pattern was observed,with five prominent crystalline peaks evidently distributed on theamorphous curve at 2θ°=15.8, 17.5, 20.0, 23.1, 24.3 and 29.3 in the70/30 blend and the blend composites. The crystalline peaks are due tothe presence of PBAT. PLA is amorphous, and merges with the amorphousregion of PBAT. The composites, however, reveal the presence of thePENP, evident by the diffraction peak at 2θ°=29.4 at d (104)=4.416 nmcrystal plane for calcite, the predominant mineral in eggshell crystalsshown in FIG. 3F.

Similar diffraction patterns have been observed in a study for PBAT/PLA60/40 and 40/60 blends. The retention of the semi crystalline nature ofthe PBAT in the blend, coupled with the crystalline PENP is verycritical to morphology related structural properties of the blend,especially, stiffness and flexibility. Crystallinity has been found toalter mechanical properties of various polymer blends to improve theirmechanical integrity.

Further, the addition of tiny shads of PENP in the matrix of the 70/30blend has the potential to alter the blend morphology for furtherenhancement of the interfacial weakness in the immiscible blend. Pastreports laid emphasis on the importance of nanoscale materials on theenhancement of inferior polymer properties.

Raman Analysis

Raman spectroscopy helps in the investigation of structure andinteractions of molecules at the functional group level. This test helpsin identifying the functional groups in the structure of the blend andassigning them to its individual components. FIG. 4 shows themicro-Raman spectra of (a) proteinaceous eggshell nanoparticles (PENP),(b) 70/30 PBAT/PLA and (c) 70/30/1 PBAT/PLA/PENP blends in the region of3200 to 200 cm⁻¹ analyzed using 532 nm laser. It is evident that thevibrational bands for the binary blend (b) and the blend composite (c)are quite similar. The assignment of these bands for Raman spectrarevealed that distinct vibrational frequencies due to PBAT in the blendappeared at 637, 3085, 1720, 1618, 1185 cm⁻¹. These are due to aromaticring vibrations, aromatic —C—H stretching, —C═O stretching, aromatic—C═C and —C—O—C stretching in the structure of the soft PBAT polymerrespectively. This conforms to the findings reported by otherresearchers. The rest of the bands in the blends are due to the PLApolyester. The bands at 709, and 860 cm⁻¹ are due to —C═O out-of-planedeformation and —C—COO stretching respectively. Also, 1050 and 1109 cm⁻¹are ascribed to —C—CH3 and —COC— stretching whiles 1395 and 2950 cm⁻¹,are due to —CH3 symmetric deformation, 1461 and 3004 cm⁻¹ are attributedto —CH3 asymmetric deformation and 1290 cm-1 is as a result of —CHbending in PLA. The spectrum for the PENP (FIG. 4a ) reveals theexistence of divalent metal ion, due to Ca⁺² at 160 and 284 cm⁻¹, C═Omode is at 716 cm⁻¹ and that due to the carbonate ion (CO3⁻²) is at 1090cm⁻¹ as reported by other researchers. The identification of bandsattributed to each individual polymer suggests that the interactionbetween the components of the blend is poor and that no new chemicalbond is established among them. The vibrational frequencies of the blendcomposite general reveal a shift by ±1 to 2 cm⁻¹. This may be attributedto the effect of PENP on the molecular motion of the functional groupsupon excitation.

Thermal Analysis/Differential Scanning Calorimetry (DSC) Results

Differential Scanning Calorimetry heating curves of PENP, PBAT/PLA 70/30blend and the blend composite fabricated by incorporating 0.5 to 2 wt. %of PENP after crystallization from melts obtained at 5° C./minutes areshown in FIG. 5. The PLA in the blend displayed a glass transitiontemperature at 60.20° C., cold crystallization at 104.83° C. and amelting point at 148.75° C. with a shoulder at 156.48° C. Also, the PBATrevealed a melting point at 122.74° C. The curve for the PENP reveals anendotherm peak at about 80° C. This is probably due to the melting ofthe protein residues in the inner layer of the eggshell used to processthe PENP. Comparing the curve in FIG. 5, It is evident that the coldcrystallization temperature of PLA slightly shifted by about 2° C.higher in the blends with much broader peaks, indicating enhanced coldcrystallizability of the PLA. It also imply that the PLA remainedamorphous and was not able to crystallize during 20° C./minutes coolingrate, as observed by Jiang et al. (2006). However, the coldcrystallization exotherm in the 70/30/2 biopolymer PENP blend appearedto have significantly reduced from those with 0.5-1.5% content of PENP.This is a sign of enhanced crystallization effect by the addition of 2%PENP in the blend. One study revealed that the addition of 0.3%, ofN,N,N-tricyclohexyl-1,3,5-benzene-tricarboxylamide (TMC-328) nucleatingagent into PLLA/PCL blend dramatically reduced the cold crystallizationpeak beyond detection, indicating that 0.3% TMC-328 could largelyenhance the PLLA matrix in the blend compared to 0.1, 0.2, and 0.5%which were also tested. This implies that optimum concentration of anucleating agent is needed to effect crystallization significantly.Also, two distinct melting temperatures were observed in the all theblends, attributable to the individual polymers, this affirms theimmiscibility of the blends as revealed in the morphological analysis.Hence, 2% PENP in this study appears to be the optimum for significantcrystal nucleation. It is also evident that high amount of PBAT lead tosignificant change in the PLA melting and shoulder peaks; suggesting thepresence of new crystalline structure induced by PBAT. This binomialmelting peak has been reported to be induced by the less perfectcrystals which had enough time to melt and reorganize into crystals withhigher structural perfection to re-melt at higher temperature.

Thermogravimetric Analysis

FIG. 6 and Table 1 provides thermal stability as determined bythermogravimentric analysis of PLA, /PBAT polymer blend system andpolymer blend composites. The amount of remaining material in thevarious neat blend (a 70:30 polymer blend without PENP) and differentblends of PBAT and PLA polymers was used to determine the thermalstability or resistance to temperature induced degradation in amaterial. In FIG. 6, the PENP curve show remarkable thermal stability,about 96% of remaining materials up to 600° C. This slight change is dueto the release of CO2 and the degradation of proteins in the eggshellbased material. The incorporation of PENP in the 70/30 blend led tosignificant improvement in the thermal stability. The followingimprovements were observed; onset of degradation, 16-46° C., _(Td50),5-13° C., _(Tdminutes), 3-7° C., _(Tdmax), 4° C. and residual yield ofabout 2-4% from the pure blend. These improvements are due to theinfluenced of thermally stable PENP embedded in the blend. As providedin Table 1, a small amount of PENP material included in the 70/30 blendas depicted in the residual yields in Table 1 led to improved thermalstability.

TABLE 1 Thermal profiles of pure and blended PBAT/PLA/PENP blend systemsOnset Residue Specimen Temp. Td50 Tdminutes Tdmax (%) PBAT/PLA 288.06 ±341.52 ± 307.61 ± 355.59 ± 1.17 ± 70/30 5.88 0.9 1.4 0.1 0.3 PBAT/PLA/310.60 ± 348.04 ± 314.10 ± 358.43 ± 3.28 ± PENP 1.36 1.0 0.6 0.9 1.0PBAT/PLA/ 307.84 ± 347.36 ± 312.23 ± 358.94 ± 4.29 ± PENP 2.77 0.3 1.40.3 1.5 PBAT/PLA/ 304.23 ± 346.23 ± 310.63 ± 358.80 ± 4.26 ± PENP 2.840.6 1.0 0.4 1.3 PBAT/PLA/ 329.09 ± 354.56 ± — 359.43 ± 4.61 ± PENP 0.850.3 0.5 0.0Mechanical Test ResultsTensile Analysis

FIG. 7 provides tensile analysis of both pure and binary blend polymersystems. In particular, FIG. 7a is the stress-strain curve representingthe general mechanical behavior of the polymeric systems under tensileload of 2.5 KN. FIGS. 7B, 7C and 7D summarize the tensile strength,elastic modulus and strain at maximum load, respectively, of the pureand binary blend polymer systems. The pure PBAT/PLA 70/30 blend showsmoderate ductility. FIG. 7A reveals that the pure polymer blend fails atabout 526% strain. The incorporation of 0.5 and 1.0% of the PENP intothe matrix of the blend shows an overwhelming increase in elongationwith a strain (%) at maximum loads occurring at 1220 and 1078%,respectively. This is an improvement of about 695 to 552% for 0.5 and1.0% of the PENP respectively compared to the pure blend. The blendsalso show distinct yielding followed by considerable cold drawing duringthe tensile test, indicating significant transformation of themicrostructure to favor ductile fracture due to blending with the PENP.The addition of 1.5 and 2% significantly reduced the ductility of theblend to ˜296 and 96% strain respectively as well as in elastic modulus.This is remarkably less than that of the pure blend, suggesting that theaddition of higher concentrations of the PENP led to significantcompromise in mechanical properties, due to the detrimentalagglomeration effects of PENP in the matrix of the blend.

Fracture Surface Analysis

The toughening effect of PENP on the ternary composite was investigatedthrough SEM analysis of the fractured surfaces after tensile tests areshown in the micrographs in FIG. 8. The fractured surface of the pure70/30 PBAT/PLA polymer blend reveals a microstructure which suggests apull out of one phase from another at the interface along the crosssection of the fractured surface. The magnified micrograph (FIG. 8B) ofthis blend show a deep crack in this uninterrupted created as a resultof the pull out and few ellipsoid phase segregations of PLA in PBATmatrix, affirming the immiscibility of the two polymers. This indicatesthat interfacial interacting is poor between the PBAT/PLA in the pureblend. However, as shown in FIGS. 8c and 8 d, the fractured surface ofthe PBAT/PLAPENP ternary composite reveal an altered morphology onfractured surface rough and tortuous surface with discontinuous crackpaths diverted around irregular fibrils of the matrix. This explains theenormous improvement in the durability of the PBAT/PLA composites with0.5 and 1.0% content of PENP. The efficiency of an elastomer intoughening a polymer in a blend is highly dependent on the interfacialadhesion and cavitation. It is known that the interfacial interactionbetween the dispersed domains and the matrix play very delicate role intoughening the blend. High toughening effect is achieved when thedispersed phase favor strong interfacial interactions with the matrix toinhibit crack growth. The phase segregation in immiscible blend therehelps in the toughening of the materials through crack path interruptionto delay failure. This effect is more evident in the ternary compositethan in the pure binary blends.

Results of PBAT/PLA Blended Film Study

Extruded compostable poly (butylene adipate-co-terephthalate)(PBAT)/agro-based polylactic acid (PLA) blend films and composites with0.5-2.0% proteinaceous eggshell nanoparticles were studied to determinethe effect of the PENP on the microstructure, thermal and tensileproperties of on a biopolymer blend. The nanostructure of the PENP wasdetermined by TEM analysis. The pure blend and composites werecharacterized using DSC, TGA, Raman spectroscopy, XRD, SEM and tensiletesting. The DSC and SEM results revealed that the two polymers areimmiscible, due to the presence of distinct melting points and phasesegregated morphologies in the blend and composite structures. X-raydiffraction revealed that the PLA is amorphous whiles PBATsemicrystalline, resulting in a semi crystalline immiscible blend. Ramanmicrospectroscopy showed frequency vibrations and intensities unique tothe individual polymers in the pure binary blend and a slight shift infrequencies probably due to the effect of the PENP on the molecularvibrations of the functional groups in the polymers. The tensile testshowed that the use of small amounts of PENP led to significantenhancement of the roughness of the ternary composite systems, withinsignificant compromise in tensile strength. Also, SEM microanalysis ofthe fractured surfaces showed heterogeneous mixtures of the matriceswith interrupt cracks paths to divert propagation and delay failure,leading to improvement in durability. The PBAT/PLA/PENP 70/30/0.5ternary composite possesses the desirable balance, strength andflexibility for flexible designs and applications.

The various preferred embodiments and experiments having thus beendescribed, those skilled in the art will readily appreciate that variousmodifications and variations can be made to the aforementioned preferredembodiments without departing from the spirit and scope of theinvention. The invention thus will only be limited to the claims asultimately granted.

The invention claimed is:
 1. A biopolymer blend comprising a combinationof three components: a) poly (butylene adipate-co-terephthalate) (PBAT);b) polylactic acid (PLA); and engineered proteinaceous eggshellnanoparticles (PENP), wherein the PENP is present in an amount ofbetween 0.5 to 2.0% wt. of the biopolymer blend; wherein the PENP arebetween the size of 10-25 nanometers; wherein the PENP are highlycrystalline, irregular, and porous; and wherein the PBAT and PLA arepresent in a 70:30 ratio.
 2. The biopolymer blend of claim 1 wherein thePENP is present in an amount of between 0.5 to 1.0% wt. of thebiopolymer blend.
 3. The biopolymer blend of claim 1 wherein the PENP ispresent in an amount of 2.0% wt. of the biopolymer blend.
 4. Thebiopolymer blend of claim 1, wherein the PENP is present in an amount ofbetween 0.5 to 1.0% wt. of the biopolymer blend.
 5. The biopolymer blendof claim 1, wherein the PLA is derived from a renewable agriculturebased source.
 6. The biopolymer blend of claim 5, wherein the renewableagriculture based source is at least one of: corn, corn starch, tapiocaroots, tapioca chips, tapioca starch, sugar beets, or sugarcane.